The main purpose of a belt tensioner that automatically responds to fluctuations in the movements of an endless belt is to prolong the life of the belt itself, or of engine components such as accessories operating in conjunction with the belt. Belt tensioners are typically used in front-end accessory drives in an automobile engine. A front-end accessory drive often includes pulley sheaves for each accessory the belt is required to power, such as the air conditioner, water pump, fan and alternator. Each of these accessories requires varying amounts of power at various times during operation. These power variations, or torsionals, create a slackening and tightening situation of each span of the belt. The belt tensioner is utilized to absorb these torsionals through use of an internally mounted torsion spring. The torsion spring is operatively coupled between an arm and a base housing of the belt tensioner so as to force a distal end of the arm against the belt and, in turn, to provide sufficient tension force, via a pulley, on the belt as required.
In some instances, the belt may experience torsional loads that are large enough to rotate the distal end of the arm of the belt tensioner away from the belt, which causes tension in the belt to be temporarily reduced. In order to counteract the large torsional loads that rotate the distal end of the arm of the belt tensioner away from the belt, the force exerted by the torsion spring in the belt tensioner is increased. The force exerted by the torsion spring may be increased by thickening the coils of the torsion spring, and/or by adding coils to the torsion spring. However, thickening the coils of the torsion spring increases the width of the torsion spring, and adding coils to the torsion spring increases the height of the torsion spring. Increasing the width or height of the torsion spring will increase the amount of packaging space required by the belt tensioner. Therefore, it may be challenging to package the belt tensioner, especially in applications where packaging space is limited.